The feature is not yet available for mobile.
Current limitations
Live transcription is currently available:
- For scheduled meetings.
- When the spoken language is U.S. English.
- On the installed desktop version of Teams.
- For customers with the following licenses: Office 365 E1, Office 365 A1, Office 365/Microsoft 365 A3, Office 365/Microsoft 365 A5, Microsoft 365 F1, Office 365/Microsoft 365 F3, Microsoft 365 Business Basic, Microsoft 365 Business Standard, Microsoft 365 Business Premium SKUs.
The feature is not available:
In channel meetings or Meet now meetings.
In GCC, GCC-High, and DoD environments.
The only option currently available is to access the transcript, if made available, after the meeting has ended.
Source: View live transcription in a Teams meeting.